Welding Nylon Strap

[AllIn]

I thought it would be a good idea to weld this strap with a soldering iron. I tested it by securing the CR atop a heavy mailing tube. I tied a 12 lb dead blow hammer to the strap and dropped it about 5'. I did this half a dozen times. I also hammered with the hammer against the connection. The strap held and showed no signs of failing. I've had a lot of negative feedback on FB rocket groups about this method. I guess the question is does the hammer drop equate to actual ejection of the Apogee Zephyr nosecone. And what is an RSO gonna think about it. Obviously, there are tried and true methods for this attachment, but I had a thought. Dang things that pop into yer head from nowhere.

 

[MarsLander]

https://www.rocketryforum.com/threads/post-a-pic-that-makes-you-go-no-no-no.183283

 

[David Schwantz]

Boy, that sure is NOT what I would do. If you want you can send them to me and I will stitch them for you. I have a German PFAFF 130 that will sew 1/4" leather.

 

[MarsLander]

The Apogee Zephyr Nose Cone, per rocksim from Apogee, weighs .5 lb.
A decent range for safety is 50G to 100G on the shock cord (above about 100g, is extreme and you would have other damage).
Therefore a reasonable force on the shock cord would be (.5 * 50G) = 25 lbf, to a max (.5*100G)=50lbf

Your drop of 12lb from 5 feet results in a velocity of about 5.5m/s and results in a force of about 66lbf. (Impact duration of .1)

I think the problem you have with an RSO, or even from a TLAR perspective is the method. It is not repeatable, nor reliable. It is also unclear what the repeated forces will do to the "melt bond" (fatigue failure), nor is it clear what the melt bond has done to the strength of the shock cord.

 

[OzHybrid]

You'll get a material change through heating that's unpredictable joint to joint. Temperature, pressure applied and time applied for. Also Nylon absorbs a lot of moisture and unless you control the humidity, the moisture will affect that weld. You could test it, and the next time it could break. There's no easy way to inspect the joint to determine if it will hold up this time.
With a sewn joint, you know the thread properties, can visually inspect the thread joint and have good confidence in the result.
Even with a knot, the properties of the strength reduction/ or not( pun ) are known (within a range)(usually). Most of the time.

 

[troj]

Everywhere you've heated the nylon, you've created a weak point. Repeated drops against it are just stressing those points, as well as doing who knows what to your "welds".

Until this is done multiple times and tested to the point of failure, you don't know what the strength of this is, or how long it will last.

A good climbing knot, on the other hand, is well quantified and you know what you're getting.

I wouldn't do this. It's too unpredictable. A lot of the goal of recovery is to improve predictability.

-Kevin